Nuclear medical imaging is widely used due to the ease of collecting multiple data sets simultaneously during an imaging period. Emissions of a distributed radioactive tracer inside an organism are collected by detectors, converted into signals, and used to generate a complete image of the organism.
Generally, in single photon emission computerize tomography (SPECT), also referred to as a gamma camera system, scintillation detectors are placed relatively close to a patient during the image acquisition process. In some respects, light rails may be placed along each side of a scintillation detector surface to provide feedback signals to a motion control system that can automatically position the scintillation detectors at the closest proximity between the detector's surface and an object being imaged, such as a patient. The placement is important as the closer the detector is to the patient, the better the image quality. Also, maintaining a patient's safety is important with respect to the detector's placement. The detectors can each weigh upwards of 1000 pounds. Therefore, the placement of the detector in proximity of the patient is such that any contact with the patient may trigger a touch sensor and shut down the motion of the detectors.
Current SPECT systems employ a two level light rail system that includes arrays of infrared light emitting diodes (IR LEDs), as shown in FIGS. 1 and 2, which illustrate a profile view and a top view of existing light rails 12a and 12b, respectively. Because each IR LED transmits its beam in a wedge shape across the surface of detector collimator 16, several IR LEDs may be arranged on both sides of the light rails in light transmitter and receiver 10a and 10b such that all wedge beams can interleave and generate a continuous plane over the surface of detector collimator 16. Generally, the IR LEDS and IR photodiodes may be sequentially scanned by a microcontroller for real-time sensing response as well as well as to prevent cross-talk between each light plane.
However, component parametric variations including sensitivity of the photodiodes and light intensity of the IR LEDs require component sorting and complex calibration scheme in order to function properly. Additionally, tight tolerance is required to assemble the IR LEDs and IR photodiodes on long printed circuit boards (PCBs) to meet the specified light plane sensitivity. Further, the PCBs are difficult to manufacture and handle.
Aside from the hardware limitations of current SPECT implementations, factors such as signal connection reliability may be compromised due to a large number of signal interfaces that are needed between the light rails and the microcontroller.